modular / modular/modular

[BUG]: Invalid code causes mojo crash

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bug mojo Needs Triage
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Mojo
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Description

Bug description
Actual behavior

Source code:
from std.memory import Pointer

def main():
var my_val = 100
var my_p = Pointer(to=my_val)
print(my_p)
print(*my_p)

Please submit a bug report to Issues · modular/modular · GitHub and include the crash backtrace along with all the relevant source codes.
Stack dump:
0. Program arguments: mojo test_0b.mojo

Crash resolving decl body at loc(“/home/diaor/Documents/Mojo/mojo-project/test_0b.mojo”:3:5)

def main():
^

Crash parsing statement at loc(“/home/diaor/Documents/Mojo/mojo-project/test_0b.mojo”:8:5)

print(*my_p)
^
Crash ParamInf::inferForCall at loc(“/home/diaor/Documents/Mojo/mojo-project/test_0b.mojo”:8:5)

print(*my_p)
^
[826545:826546:20260604,172643.799882:ERROR directory_reader_posix.cc:42] opendir /home/diaor/Documents/Mojo/life/.pixi/envs/default/share/max/crashdb/attachments/84bfce90-37d9-499e-becd-d271814d3098: No such file or directory (2)
#0 0x000056377eb766ab (/home/diaor/Documents/Mojo/life/.pixi/envs/default/bin/mojo+0x80926ab)
#1 0x000056377eb737ca (/home/diaor/Documents/Mojo/life/.pixi/envs/default/bin/mojo+0x808f7ca)
#2 0x000056377eb772f7 (/home/diaor/Documents/Mojo/life/.pixi/envs/default/bin/mojo+0x80932f7)
#3 0x00007fa84293d520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
#4 0x00007fa842a1990d syscall ./misc/../sysdeps/unix/sysv/linux/x86_64/syscall.S:38:0
#5 0x00007fa842c23a23 (/home/diaor/Documents/Mojo/life/.pixi/envs/default/bin/../lib/libAsyncRTMojoBindings.so+0xd2a23)
#6 0x00007fa84293d520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
#7 0x000056378dd3bdd0
Segmentation fault

Expected behavior

Compiler reports error on this code

Steps to reproduce
  • Please paste or attach the .mojo files that are needed to reproduce the issue.
  • If you are able to reduce the reproduction steps to a small example, this would be much appreciated!
  • Please quote the command line you used to compile and/or run the example.
  • If you see a crash or an error message, please paste it in the "actual behavior" above.
  • If using the Godbolt / Compiler Explorer, share the example link.
  • Include anything else that might help us debug the issue. Your insights and observations are welcome!
System information
  • Provide the system information by running pixi info.
  • Provide version information for MAX (includes Mojo) by pasting the output of pixi list max.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by running mojo test_0b.mojo with the reproduced source and inspect the crash locations reported around main() and print(*my_p). Compare the compiler behavior with the expected diagnostic for invalid code; done means the input reports an error instead of crashing or producing a segmentation fault.

Written by the indexing model from the issue text.

Assessment

Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Clearly specified
Newbie friendliness
45/100

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